Category Sound

          Bats are fascinating animals that have many unique features. One of these is the ability to sense a prey location using sound. Confusing, isn’t? Let’s get to know how they do it.

          Bats use the sound technique known as ‘echolocation’. It means determining the location of something by measuring the time it takes for an echo to return from it.

          As they fly, bats make calls, and listen to the returning echoes to build up a sound map of their surroundings. These sounds are produced by contracting their larynx. Measuring the time it takes for the echo to return, this smart mammal can predict at what distance its prey is!

          Usually, the calls of bats are pitched at such high frequencies that humans fail to hear them naturally. Another interesting fact is that bats can distinguish between obstacles and preys through echolocation, and can thus avoid the obstacles and catch the prey.

          How many of us have seen birds that don’t make sounds? Not many. Birds are in fact, most known for their ability to make sound, be it sweet chirping, or harsh caws.

          While humans and other mammals produce sound from the voice box or larynx, birds have a different organ for sound production – the syrinx. Located near lungs, it is a double voice-box that consists of a resonating chamber, and numerous membranes. As air flows over them, the membranes move back and forth, producing sound.

          There are different frequencies at which bird sounds come out. There are other birds too that can sing in high frequency ranges, like warblers, sparrows, wax-wings, kinglets etc. It is believed that one can never stop a bird from learning its own species’ song.

          Interestingly, many species have at least some mimicked sequences in their most common songs and calls.

               For a long time, it was believed that oceans were silent places. But, as science advanced, it was proved that most of the animals living in waters cannot survive without sounds. 

               We know for a fact that light reaches only till the surface of water. In the case of smell, it fails to spread far from their source, while under water. Contrary to this, sound waves find their ideal medium in water, and travel faster than in air. They move greater distances, and at the surface of water, get reflected back into the depths. That is why even the sound of surf crashing on to a rocky beach travels far into the ocean.

               In general, sounds help most marine animals to sense their surroundings, communicate, locate food, and protect themselves.

               Mammals like whales, for instance, identify objects like food and obstacles using low frequency pulse signals. Dolphins communicate through clicks and whistles. They use the technique of echolocation to detect and characterize objects.

          Sounds become part of a bird’s life from the very moment they are born.

          It is wrong to think that the only sounds made by birds are songs. There are a variety of others too, like alarm calls, begging calls, contact calls, flight calls etc., used by them, depending on the circumstances.

          Songs are of course the most distinctive and familiar sounds. They are used mainly to attract mates, mark their territories, or discourage intruders. The quality and duration of a song depend on the species. Some may have different songs for different times of a day, but some sing only in the morning or evening. The yellowhammer, for instance, repeats its song around 1000 times a day.

          Begging calls are usually made by young birds to draw attention. Contact calls, on the other hand, are used to signal one another, particularly while travelling in a flock.

          In addition, there is something called the dawn chorus. It occurs when a large number of birds sing at the start of a new day. This is done either to protect a territory, or to call in the flock.

          Whales are in general, highly social creatures that move under water in groups called ‘pods’. To communicate and socialize with each other, they use different kinds of sounds; namely, clicks whistles and pulsed calls. Let’s see what these sounds are, and how they help the marine mammals.

          Clicks are made by whales for purposes of navigation and identification of physical surroundings. They also help to distinguish between friendly creatures and enemies.  

          The other two sounds- whistles and pulsed calls- are exclusively used during social interactions. The latter which are similar to squeaks, or screams, is rather more frequent.

          Surprisingly, there are differing vocal dialects existing between different pods. Perhaps this is why whales can differentiate between familiar whales and stranger whales.

          In addition to the above mentioned sounds, the marine mammals also make loud slapping sounds on the surface of the water, using tails and fins. This can be heard for very long distances, and are thought to be warning signs, or a tool to scare other smaller fishes. 

               The list of the best ‘singers’ among mammals can never be complete without humpback whales. These aquatic animals are capable of producing complex series of sounds that are close to songs. The whale songs, as they are popularly called, consist of a variety of loud, low-pitched tones, moans, whines and grunts that are often melodious in nature.

               But most importantly, the songs have themes that are sung in a precise order, and change slowly over years.

               The songs typically last 8-15 minutes, and are repeated for several hours at a stretch.

               Unlike other ‘singers’, humpback whales do not produce sound through vocal cords, simply because they don’t have any. Their songs are created when air is pushed out of the blowhole located on top of the animal’s head.

               Interestingly, some male humpbacks, like the North Atlantic ones, can be heard singing the same song together even when they are miles apart.